U.S. Pat. No. 6,041,499 discloses a method wherein a cylinder housing is cast having a cylinder wall which delimits an interior space for accommodating a reciprocating piston. The cylinder is provided for a two-stroke engine and therefore transfer channels enclosed in the cylinder wall are provided. The combustion chamber is delimited by the piston. The supply of the combustion chamber in the cylinder with the fuel mixture or air is ensured via the transfer channels in a manner known per se. The transfer channel runs essentially axially in the cylinder wall and, to connect the transfer channel to the interior of the cylinder, a radial control window is provided in the cylinder wall which is cyclically covered and again cleared by the stroke piston during operation of the engine.
In the known method, a blank of the cylinder housing is first cast which is provided only with the flow channels enclosed in the cylinder wall so that the blank cylinder body can be cast with a high degree of efficiency and a savings of manufacturing costs. In a second method step for making the cylinder, a control window is machined in for each transfer channel with a non-contact machining process, for example, an electric discharge machining process. The known method assumes that a precise machining in the formation of the control window in the cylinder wall is only possible with a non-contact machining process. In the known non-contact machining process of the control windows, a work tool is introduced into the cast blank cylinder body and is brought into position at the wall section of the cylinder wall where the control window is intended to be cut out in the cylinder wall for connection with the still hidden transfer channel.
The manufacture of cylinders with the known method, however, requires costly processing machines to effect a non-contact cutting out of the control windows in the cylinder wall. In the manufacture of cylinders for small internal combustion engines such as those used in portable handheld work apparatus, the non-contact machining leads to high manufacturing costs of the cylinder and therefore of the engine. This is especially unacceptable when manufacturing in large quantities.